MP2611 – 2A, 1-CELL SWITCHING CHARGER FOR USB AND ADAPTER POWER

MP2611 Rev. 1.12

www.MonolithicPower.com

13

12/7/2012

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Charge-Full Termination and Auto-Recharge

When the charge current drops below the

phase, the charger ceases charging and the

STAT1 -pin becomes an open drain. The timer

will also be reset and turned off. If the battery

voltage falls below 4.0V, auto-recharge begins

and the timer restarts a new charge cycle.

Charger Status Indication

outputs that must connect to the VREF33 output

or some other bias power supply through pull-up

resistors. Their output logic level combinations

indicate three status of the charger:

Table 1: Charging Status Indicator

STAT2

STAT1

Charger Status

Low

Low

Charging

Low

High

End of Charge; Faults

(Thermal Shutdown;

Time-Out; NTC Fault)

High

High

Input Power Absent;

EN

Disabled

Safety Timer Operation

The MP2611 adopts an internal timer to

terminate charging if the timer times out. An

external capacitor on the TMR-pin programs the

timer duration.

The trickle mode charge time is:

TMR

Trickle_tmr

C

t30

(minutes)

0.1μF

=×

The total charge time is:

TMR

Total_tmr

C

t

=3

(hours)

0.1μF

×

TMR-pin to GND. The timer can be disabled by

pulling TMR to GND.

If a timer-out event occurs, the charging will be

terminated and the

drain to indicate the fault.

The charger can exit the timer-out fault state and

initiates a new charge cycle when one of the

following conditions occurs:

(a) The battery voltage falls below the auto-

(b) A power-on-reset (POR) event occurs;

(c)

Negative Thermal Coefficient (NTC)

Thermistor

The MP2611 has a built-in NTC window

comparator that allows it to sense the battery

temperature via the thermistor packed internally

in the battery. It ensures a safe battery operating

environment. Connect an appropriately-valued

resistor from VREF33 to the NTC-pin and

connect the thermistor from the NTC-pin to

AGND. The resistor divider with a dividing ratio

depends on the battery temperature determins

the voltage on the NTC-pin. Once the voltage at

the NTC-pin is out of the NTC window, the

MP2611 stops charging. The charger restarts if

the voltage re-enters the NTC window range.

Short Circuit Protection

The MP2611 has an internal comparator to check

the device detects a battery-short status and the

cycle-by-cycle peak current limit falls to about 2A

to limit the current spike during the battery-short

transition. Furthermore, the switching frequency

also folds back to minimize the power loss.

Thermal Shutdown Protection

To prevent the chip from overheating during

charging, the MP2611 monitors the junction

the charger converter turns off. Charging restarts